Understanding the Code: Differentiating Between Process and Program in C++

Sachin Bhatt

I'm studying the concepts of processes and programs in C++ on Scaler and came across the following code snippet:

#include <iostream>
#include <cstdlib>

int main() {
    std::cout << "Hello, World!" << std::endl;
    return EXIT_SUCCESS;
}

While the code is a classic "Hello, World!" example, I'm struggling to grasp the distinction between a process and a program, especially in the context of this code. Can you explain how this C++ code represents both a process and a program? Additionally, could you highlight any specific elements in the code that demonstrate these concepts?

JonB

@Sachin-Bhatt
Personally I don't think C++ has much to do with a "process" or a "program". It's a programming language. From those you can produce a "program"/"executable", by some means. A "process" is just the name usually used for when a host OS executes a program of some kind or another, loosely.

P.S.
It seems to me your link describes in detail where it sees the boundaries between "process" and "program". Can't add much to that. All seems intuitive to me, don't know what more than there to say. A program is what you build from your source (run gcc to compile and then link to a.out) and a process is how the OS runs it (run ./a.out. Simplez :)

P.P.S.

highlight any specific elements in the code that demonstrate these concepts?

For an exam question, it might be worth mentioning that because this code chooses to define a function named main() in C++ it will be acceptable as a complete program, it can be executed. If the function had been named anything else, say fred(), it would not be executable (by default from C++, you'd have to ask for some odd linker stuff if it can be done at all). main() is special in C++ (and has equivalents in other languages).

SimonSchroeder

Simply said a program is an (executable) file on your computer. (People also say: "I wrote a program." In a sense the source code itself which can be compiled and linked into an executable could be seen as the program. This is more evident in scripting languages like Python where there is only code and no executable.)

If you launch a program the OS will create a process that the program can be run in. A process is an OS concept and simply put it is only a separated context for programs to run in managed by the OS. Most programs will only use a single process. Though in general a program can fork a new process and now runs in two separate parts. However, even though a program can instantiate a new process, the two processes do not have a shared state.

In your simple "Hello, World!" example your code (or even better: your compiled code) is the program. If you launch the program, a process is created to run the program. Once the program finishes execution, the process will end. Like the link you provided states: A process is an instantiation of the program. (If you know already object oriented programming this might help: A program is like a class. If you instantiate the class you get an object. In the same way if you instantiate the program (through launching it) you get a process. Just as you can have multiple objects of the same class, you can run a program several times in parallel–each in its own process.)

mzimmers

@Sachin-Bhatt said in Understanding the Code: Differentiating Between Process and Program in C++:

Can you explain how this C++ code represents both a process and a program?

To add to what the others said, code is never a process. Source code like yours is built (compiled and linked) into a program (something that can be run). A process is something the OS furnishes for your program is built.

It might help to think of it this way: if all computers in the world ran the same OS, you could build your program, and distribute to millions of people everywhere. Every time they run it, they create a process on their system, but it's the same program (the bits in the executable file you distribute are identical).

Hope this helps a little...